Brown Algae, Diatoms, Or Something Else?

My tank has been running for about 3 months now. My water tests have been stable for about 3 weeks now. 0 ammonia, 0 nitrite, 5 < nitrate, pH of 7.5. I am getting brown specs on the front glass. They are very small flat circles and cannot be wiped off easily with my finger. I literally have to go over one spot for a good minute with an algae scrubbing pad to wipe it off.

100g tank with canister filter and a powerhead. Plenty of water movement. I run 2x 48w t5 lamps and a Current Satellite Pro Plus LED lamp for 8 hours. I have live plants (not many. plan to add more) and use all-in-one liquid fertilizer once a week and a daily dose of metricide for CO2. Before dosing with Metricide, I had green algae, brown algae and also had brown beard algae growing on driftwood. Once I started dosing, all the algae growth stopped. But now I'm getting these tiny brown spots on front glass that are hard to wipe off. Any ideas?

 

Can you take a pic of it? Diatoms are usually easy to remove.

 

I'll try to take pics once the lights kick on in an hour or so.

 

Well I tried taking pics but unable to take one that actually focuses on the tiny spots. My phone cam is no good. But getting close to the tank I am now noticing green algae on glass as well. The brown spots are barely noticeable now. Seems I now have a different issue. I'm guessing because I currently have so few live plants the algae is feeding off the fertilizer quicker. Should I buy more plants and cut back on fertilizer meanwhile?

 

Green spot algae is another thing entirely. That would fit the description of being hard to get off. I would add more plants and lower lighting. Ferts shouldn't be the issue.