Discovered this today

Another one

They're also chlorotic - the browning may be another symptom of what is causing that. Which will be a minerals related problem, for example iron.

Thank you Embothrium and Ken Adrian!

I fertilized them very lightly because the plants looked starved, but I didn't want to overdo it. Maybe I should go heavier on the fertilizer?

And no, I haven't spent more money on the remedies. It's all stuff that I always have to hand.

There seems be a lack of clerodendrum inerme plants at the nurseries I buy from, plus it was the end of lockdown with uncertainty over the advent of yet another lockdown, so I just went ahead and bought the lot, hoping to nurse them back to health.

Need to figure out what is causing the chlorosis and address that specifically. For instance if it is an iron deficiency you need to be applying iron rather than a random general fertilizer product - if the latter is what you have been using.

If you have an independent garden center in your area take some of the affected material to them and ask about it. If they think an iron deficiency is likely they will probably have a product in stock you can use to correct it - outlets in my area even have these and we are not a region where alkaline soils make this problem frequent.

Thanks!