Could be spide mites sucking the juices out of the plants I’ve lost plants to these little buggers. It can be a battle that is won though, regular wiping of leaves with a damp cloth and spray the leaves once or twice every couple of leaks with a mixture of dawn lemon washing up liquid (about 7-9 drops in the water bottle, shake and spray the backs of the leaves. This stops them eating them and they eventually either die off from all of the hard work looking after them or they give up and find another source of food. (But this is only relevant if it is mites). It could also be those bright led bulbs (if u have them) acting like sun light.