First algea in new pool/spa

We've had our IG gunite pool/spa for nearly a year now and everything's been fine until today, when we noticed green algea (quite a bit, actually) growing in the spa on the drain cover and spa light. It's not in the pool (yet?) but I'm worried because this seemingly sprang up overnight (perhaps it's been there a day or two, since we don't always look in the spa, but no longer).

So I come running here before I run to the pool store for advice -- since I'm a total newbee at this, and since my chemistry in the pool seems fine, what do I do? Does it make a difference that we've been keeping the pool at around 88 degrees for the last couple of months?

We have a salt chlorinator and it's running at 90% right now but all levels seem fine.

Post some current water testing results from a drops based kit and then somebody here can take a look and offer some advice. You are so smart coming here first before going to the pool store for advice!

My kit ran out two weeks ago and I haven't bought another (on my to-do list but I was in the hospital...) But I did write down my results back then if it helps:

CYA 60
Tot Chlorine: 1.7 (and that was when I bumped up the salt-chlorinator to 90% from the 75% it had been at)
Free Chlorine: 1.7
Ph 8.4: (I added 5 pounds of Lo and Slo to the pool after that)
Minerals 2500
Total Hardness 388

Is there anything else anyone might need. And, in the meantime, should I scrub or vaccum off the algea off the spa? (I have zero experience with this now). Oh, and the water is crystal clear in both pool and spa, if that makes a difference.