First time grow indoor royal dwarf RQS

Check under the leaves with a magnifying glass for mites and eggs. The mites will look blackbrown and they are very hard to spot. If you see any small spots..keep youre eye on it for a minute to see if it moves. The easiest way to check for them is to leave the plant undisturbed so they get a chance to make webs and then spray the plant with water from a fine mister. The water clings to the webs and makes them easier to see. As your plants are in flower... go easy if spraying them to avoid water affecting the buds in a detrimental way (bud rot). I would never reccommend spraying plants that are in flower, only if absolutley necessary or if you want to identify a problem. You've got many options if it is spidermites but whatever you choose, do it quick because their rate of reproduction is very high and they can devestate ur plant given the chance. If u have the cash and they are available, I would recommend introducing some natural predators of spider mites. If u can get hold of any ladybirds (ladybugs...whatever), they do a fantastic job of eating the spider mites and do no harm to the plant.

I had the same problem. Overwatering and the roots can’t breath thus cant take nutrients from the soil, is the soil really humid?

Nitrogen problem, perhaps a little calcium too. Tell me if you need more help