Bottle carbonation - yeast raft or infection?

[WeatherWithYou]

From the looks of your bottles on your original post it looks as though perhaps too much oxygen in your bottles and the yeast is still working. 3 things I try to do in every batch I brew. 1. Sanitise. 2. Use high quality yeast. Often discard the yeast that comes with extract kits. 3. Keep the brewing temperature constant.
The yeast that comes with Morgan’s Blue Mountain lager is not a lager yeast but rather an ale yeast so you can brew it at higher temps but in reality a fermentation fridge with a temperature controller should be a priority to give constant great results. I double my yeast when doing lagers but have never found under pitching a problem when brewing ales. Cold crashing works well with both lager and ales and I do a diacetyl rest on both types of brews.

Thanks for this. Yep, I went with the ale yeast on the bottom of the tin instead of the lager yeast that came with the full kit specifically because I had no temperature control. I'm saving it for winter. I will eventually invest in a fridge but I literally have no room for it right now, so I'm making do and having fun doing it.

This beer thankfully has shown no signs of infection - it's matured into a fairly clean beer, with some nice, though subtle, fruity flavors and aromas. There's just a hint of something a bit off remaining, but it reminds me of the aftertaste of a Coopers Pale rather than anything truly off-putting, just not quite what I wanted for the beer. Also no signs of diacetyl.

I've since invested in some higher quality yeasts - my second batch used Kveik and fermented consistently around 30-35 degrees. I've had a couple of bottles and so far they are under carbonated but they've only be bottled a little over a week, and they actually suit under carbonation well... almost like a fruity new world take on an British bitter.

I've got my third beer fermenting now, and while I probably should have spent more time on the basics, after a bit of research I went for a no boil, GF sorghum extract Philly Sour saison (staggered pitch with Belle Saison). Depending on how it turns out I might share the recipe, but so far (mid fermentation) it's tasting surprisingly great. I used some wet towels to protect it on a couple of hotter days, other than that it's been fine where I am, typically 22-24 degrees. Now that the Belle Saison is taking over I'm less concerned about temp.