Is this an exception to the rule "don't sell lower than you bought?"

You have 3 fund indexes, A B and C

You started exactly 1/3 invested in each at the beginning, but without rebalancing

All 3 of them plunge, but

A drops 7%

B drops 57%

C drops 60%

Latest outlook is extremely favorable to a B and C recovery
But you have no additional funds to invest with

Can you take from Fund A and allocate to B and C Eventhough it would mean you bought high and sold lower?


Is this an exception to the rule "don't sell lower than you bought?"