Light source change stress?

Yes of course, different wavelength, different strength, different heat. Turn the led down or raise the height and gradually increase over week or two. The plants need to reclimatise their selves 🌱👍

The Mars TS1000 is a good light (I grew a killer LSD plant under one) but it is half the wattage of the 300W light you replaced. I suggest you download the Photone app and measure your DLI. Seedlings don't need much - around 20 if I recall correctly. This app has allowed me to keep my lights dialed in to the correct DLI for each life stage of your plant. NB: The settings in Photone are important. Other growers have tested this against good light monitors and have found the app is most accurate when you use the "sunlight" setting - NOT the setting for LEDs. If you have an Apple phone, you need to put some plain white paper over the camera to act as a diffuser. I have an Android - they don't need that, only the Apples. Also, be sure to set the time setting for the number of hours you're using. Good luck on your grow!

if intensity is drasticalyl different... it'd be like taking an indoor plant and putting it in direct sunlight... wilting is likely to occur. Doesn't mean it can't adapt to it.. a little trial and error as you ramp up intensity... try to make notes of your distance from canopy and %-power if it has a dimmer... it will make adjusting over time easier if you know what you previously used and what resulted. Remember what you use for seedlings, young vege, mature vege and after 12/12 flip, if a photoperiod. hours of use is obviously proportionally important too. when you hear "you need 150% more light in bloom" that's relative to 18hours vs 12 hours of light... not because teh plant changed or needs more... it can still handle the same energy per 24 hours, relative to environmental factors -- temp, RH% and atmospheric CO2. it's difficult to say 'do this with your light" because there are many variables to account for. Use the plant's behaviour to dictate what you do with light.. too mcuh stretch needs more. The opposite needs less. If what you see is caused by change of intensity, reduce and slowly increase until you run into issues again... make sure it recovers before drawing conclusions from what you see. find the 'edge' and step back a bit, figuratively speaking..

Even your basil is overwatered ;))) Give good humidity, can bet yours is in 50 or lower. You need 70 now. Light stress can happen, they can be stunt, they could be killer with too intense light. Imagine your plant almost at harvest, he uses 100% of light, so your current size is how much smaller ??? Somewhere in that proportion is healthy easy answer. Any lux app for mobile and 20000 lux max at top level leaves in veg, even 15 k better if you want to grow not midget ;)) All the best !

going from a CFL to a LED can cause some stress but your plants not looking to bad TBH. I don't see sign of light stress. The downward pointing leaves can be a sign of over watering. If its really bad, the new leaves become mutated and blistered. Keep an eye on it and use the recommended heights for the new LED as they will be different then the older CFL. Light stress will look like burning on the new leaves, best to avoid getting the leaves wet as well when watering as that can cause some bleaching spots on them. In good news a full spectrum LED has a better overall spectrum then the CFL Nice Upgrade! Best Of Luck and Happy Growing!