It's natural and so long as you don't see any serious deterioration in their health is nothing to worry about.
1-2	It's	_	_	_	_	_	_	_	_
1	It	it	PRON	PRP	Case=Nom|Gender=Neut|Number=Sing|Person=3|PronType=Prs	3	nsubj	3:nsubj|19:nsubj	_
2	's	be	AUX	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	3	cop	3:cop	_
3	natural	natural	ADJ	JJ	Degree=Pos	0	root	0:root	_
4	and	and	CCONJ	CC	_	19	cc	19:cc	_
5	so	so	ADV	RB	_	6	advmod	6:advmod	_
6	long	long	ADV	RB	Degree=Pos	19	advmod	19:advmod	_
7	as	as	SCONJ	IN	_	11	mark	11:mark	_
8	you	you	PRON	PRP	Case=Nom|Person=2|PronType=Prs	11	nsubj	11:nsubj	_
9-10	don't	_	_	_	_	_	_	_	_
9	do	do	AUX	VBP	Mood=Ind|Number=Sing|Person=2|Tense=Pres|VerbForm=Fin	11	aux	11:aux	_
10	n't	not	PART	RB	_	11	advmod	11:advmod	_
11	see	see	VERB	VB	VerbForm=Inf	6	advcl	6:advcl:as	_
12	any	any	DET	DT	_	14	det	14:det	_
13	serious	serious	ADJ	JJ	Degree=Pos	14	amod	14:amod	_
14	deterioration	deterioration	NOUN	NN	Number=Sing	11	obj	11:obj	_
15	in	in	ADP	IN	_	17	case	17:case	_
16	their	their	PRON	PRP$	Case=Gen|Number=Plur|Person=3|Poss=Yes|PronType=Prs	17	nmod:poss	17:nmod:poss	_
17	health	health	NOUN	NN	Number=Sing	14	nmod	14:nmod:in	_
18	is	be	AUX	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	19	cop	19:cop	_
19	nothing	nothing	PRON	NN	Number=Sing|PronType=Neg	3	conj	3:conj:and	_
20	to	to	PART	TO	_	21	mark	21:mark	_
21	worry	worry	VERB	VB	VerbForm=Inf	19	acl	19:acl:to	_
22	about	about	ADP	IN	_	21	obl	21:obl	SpaceAfter=No
23	.	.	PUNCT	.	_	3	punct	3:punct	SpaceAfter=No
