Just had tubes replaced like 3 months ago worked pretty good then, but lately I've been getting some different sounds coming out of it. Earlier today it was like a crackling like popcorn being made noise. So I took out the tubes and sprayed a little bit down the holes to maybe clean them out a bit. Now instead of the 1st and 3rd tube glowing blue, it's just the first one and the crackling noise has reduced a bit. But I am playing now and I hear a faint high pitched ringing coming from the head. What could be the problem?

The amp head has always been kind of quite to begin with, even compared to my buddy's valveking; It has an alright tone still though. I've checked all my cables and they all seem to be good, and I've checked cabs and I know it's just my head.
while the amp is on and audible tap the tubes with something wooden, like a chopstick or pencil

tubes can go bad after even only 3 months. not often, but definitely not rare either
'87 Fender Strat
Oscar Schmidt Archtop
Laney LC15R
it should make the noises more prominent, which would mean your tube(s) are microphonic

i will mention that my combo had the same problem until eventually it stopped making any sound even though it turned on.
I took it to a tech and somehow a resistor went bad in the preamp section

you might want to have a tech take a look at it, if it turns out that its something other than a microphonic tube like boardsofcanada is mentioning
the sound of the pencil tapping being amplified meaning your tubes are becoming/are harmonic = get new tubes

edit: damn im slow
Jackson DK2M Dinky Pro W/ EMG 81/85 18v Black
ESP LTD EC-1000 W/ EMG 81/60 See Thru Blue
Schecter C-1 HellRaiser W/ EMG 81TW/89 Black Cherry
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