deficiencies in flowering

Hi guys, first time growing currently on the 3rd week flowering and noticed new leaves with brown spots as seen in the photo possibly needs calmag but not sure as found could also be fungus? Appreciate any helpt

Just noticed some of my fan leaves are really thinned out (adjusting pH / ppm to help W that)— and some have these white bumps on them. Are these eggs? Have no idea. Any help is appreciated!

The leaf tips on this one plant are browning. Im limited in terms of feeding because i am trying to control fungus gnats that came from another grower…any idea whether this is a concern or just part of the plant’s aging. Its about 38 days into flower and over 100 days old. Its a sativa...