The last water tests before the chalking have shown that oxygen levels look like they are increasing significantly (8.9 mg/L at 73 % saturation). This is a really good sign and may be linked to the reduction in suspended organic matter in the lake.
Ammonia level are still increasing, but are more or less similar to last week (0.48 mg/L, at pH 7.9, 6.3 °C), so this may also be stabilising.