what deficiency could it be for now I am watering ...

Nitrogen (N)

Nitrogen to start. You need to foliar feed some nutes back into that plant ASAP.

Hungry for all macro nutrients......nitrogen, phosphorous and potassium. In other words, generally under fed.

That is a nitrogen deficiency if it started at the bottom. and is going up the plant. This could be from ph out of line or overwatering. If overwatering was a issue prior, it could be rot in root system. Hard to diagnosis with no diary information to review.

Hey there no worries , it looks like over watering more than excess of nutrient , I guess you flush them with good PH water no nutrients to get them well soon again ! 🤟🏽

looks like it needs more nitrogen. if you have multiple parts to your fertlizer mix, try to increase the one that impacts N the most while impacting others the least... it is paling from bottom up on plant and from the tip and in... I don't see coinciding symptoms, so this is pretty cut and dry. React relative to pace of progression. If this has been happening slowly, start with a small bump and see what happens. even after it seems 'fixed,' keep eye on it drifting the other way. If the leaves get too lush you know to dial back a bit. You also know where you ran into problems for deficiency before, if you track the doses you feed over time. Soil is a bit more of a guess, but still worth tracking. the longer you go the more you are depending on fertilizer as nutrients in soil are tapped out. you may need more across the board before long, if that is the case here. notes can help preempt such a transition and avoid problems in future. plant always dictates despite best laid plans of mice and men :P as far as the red - could be progression or genetics.. the rest of the plant doesn't show it.. you might see reds as senescence kicks in -- 'fall colors' Less than 68F or so temps can bring it out too. the necrotic spots are just very advanced n-deficiency, since that's the only place you find them is on a leaf that's about to be shed from plant.

can be: watering problem, temperature , nutrient deficiency.... with more info whats going on in ur tent will be better