Mangel ?

Just a side note, whether it's the virus or not, simply claiming that it's impossible to get it... you can also get the virus without tobacco soil... that's probably the smallest transmission route. The tobacco mosaic virus discovered in 1892 is the most well-known and commonly occurring virus in cannabis and infects many other crops besides tobacco plants, such as peppers and tomatoes. It is a "Contagium Vivum Fluidum," or an infectious, soluble pathogen that is mechanically transmitted. The virus is also quite persistent and remains stable for a very long time. In dried tobacco, it can survive for up to 100 years and easily transmits. For this reason, smokers are often not welcome on plantations and in breeding experiments. By the way, the hemp mosaic virus (HMV) is also related to TMV, which, along with the hemp streak virus (HSV), is one of the plant viruses studied in cannabis plants. The hemp mosaic virus is a so-called cowpea strain of TMV, so one can assume that the symptoms are similar. Infection by the mosaic virus is especially likely in summer and autumn when many winged aphids are in season, carrying the virus. Other plants can also be carriers. Thus, cross-infections are not uncommon (from hemp plants to tomatoes and vice versa). It can also happen that plants are silent carriers – meaning they are infected and transmit the virus even if they show no symptoms.

This is not nutrient related, if it was, all/many leaves would show the symptoms. The strange leaf in the picture is just that, "strange" and you really do not have anything to worry about. No cannabis plant will ever have 100% perfect leaves, 100% of the time. Also it is definitely not tobacco mosaic virus, which is almost impossible to get, unless you transport infected soil from a tobacco field into your grow tent.

I don't think there is any lack of nutrients, I would give some vitamins and amino acids and maybe a little cal-mag because I think that maybe your light is already weak for further growth, but you better wait until someone who grows indoors calls you, I only grow outside. Happy Grow!!!

Hard to say, it could be the tobacco mosaic virus, but that's really just a guess. I would keep an eye on it and wait a bit; maybe it will get better. If it gets worse, you can upload more pictures.