right before your next WC take an old gift card and scrape as much of it as you can off then suck it all up it looks like a bit of diatoms as well as some green algae. The sooner you remove it the better.
I've remove fish to a separate tank using half the water from that tank & then clean the algae tank & decor with a hose & rock salt.
My algae blight, it was in the gravel too. Check gravel before cleaning, if there's no algae , then save the gravel with it's beneficial bacteria and don't use regular water & salt on it.
because you saved half the water, less chance of shock to fish. i tried for a month to clean algae & it was only way to fix it. Now I only leave light on 6 hours a day ( it had been 12-14 before)
It was my 4 female, 1 male community betta tank +1 snail. No deaths. i rinsed out rock salt 3x in tank after clean, so no alt remained ( I didn't want snail to die.)
algae killing solution helped but did not clean it enough. I have a 12 inch scraper and that helped but did not stop it.
Only a full clean & less light worked. Mine was just green algae though. Good luck